The orbital ephemeris of the classical nova RR Pictoris: presence of a third body?

TL;DR

This study refines the orbital period of RR Pictoris and suggests the possible presence of a third body affecting its light curve, proposing future observations to confirm this hypothesis.

Contribution

It provides a precise orbital ephemeris for RR Pictoris and explores the potential influence of a third body on its orbital dynamics.

Findings

Derived a new orbital period of 0.145025959 days.

Detected systematic deviations in the O - C diagram.

Suggested a possible third body with a 70-year orbit.

Abstract

The ex-nova RR Pic presents a periodic hump in its light curve which is considered to refer to its orbital period. Analyzing all available epochs of these hump maxima in the literature, and combining them with those from new light curves obtained in 2013 and 2014, we establish an unique cycle count scheme valid during the past 50 years, and derive an ephemeris with the orbital period 0.145025959(15) days. The O - C diagram of this linear ephemeris reveals systematic deviations which could have different causes. One of them could be a light-travel-time effect caused by the presence of a hypothetical third body near the star/brown dwarf mass limit, with an orbital period of the order of 70 years. We also examine the difficulty of the problematic of detecting sub-stellar or planetary companions of close red-dwarf white-dwarf binaries (including cataclysmic variables), and discuss other possible mechanisms responsible for the observed deviations in O - C. For RR Pic, we propose strategies in order to solve this question by new observations.